Chemistry is sometimes called "the central science" because it bridges other natural sciences like physics, geology and biology with each other. Chemistry is a branch of physical science but distinct from physics. The etymology of the word chemistry has been much disputed. The genesis of chemistry can be traced to certain practices, known as alchemy, which had been practiced for several millennia in various parts of the world, particularly the Middle East. Chemical reaction engineering (reaction engineering or reactor engineering) is a speciality in chemical engineering or industrial chemistry dealing with chemical reactors. Frequently the term relates specifically to catalytic reaction systems where either a homogeneous or heterogeneous catalyst is present in the reactor. Sometimes a reactor per se is not present by itself, but rather is integrated into a process, for example in reactive separations vessels, retorts, certain fuel cells, and photocatalytic surfaces. It has been endeavour of authors to present to the Engineering graduate students the fundamental principles of chemistry, as well as their relevant technical applications, in a crisp and easy to understand way. It is the fervent hope of authors that this book would serve a useful purpose. Comments for further improvement of this book will be gratefully acknowledged.